Bandpass filters for bands n77 and n79 must be capable of handling the transmit power of the communications device. Both band n77 and band n79 use time-division duplexing (TDD), such that a communications device operating in band n77 and/or band n79 uses the same frequencies for both uplink and downlink transmissions. Two of these new communications bands are n77, which uses the frequency range from 3300 MHz to 4200 MHz, and n79, which uses the frequency range from 4400 MHz to 5000 MHz. The 5G NR standard defines several new communications bands. Radio access technology for 5 th generation mobile networks is defined in the 5G NR (new radio) standard. Radio access technology for mobile telephone networks has been standardized by the 3GPP (3 rd Generation Partnership Project). The desire for wider communication channel bandwidths will inevitably lead to the use of higher frequency communications bands. However, these existing technologies are not well-suited for use at the higher frequencies and bandwidths proposed for future communications networks. High performance RF filters for present communication systems commonly incorporate acoustic wave resonators including surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, film bulk acoustic wave resonators (FBAR), and other types of acoustic resonators. These improvements can be realized at many levels of the wireless system both separately and in combination, for example at the RF module, RF transceiver, mobile or fixed sub-system, or network levels. Improvements in RF filters can be leveraged to provide system performance improvements such as larger cell size, longer battery life, higher data rates, greater network capacity, lower cost, enhanced security, higher reliability, etc. Performance enhancements to the RF filters in a wireless system can have broad impact to system performance. Specific design and manufacturing methods and enhancements can benefit simultaneously one or several of these requirements. RF filters typically require many design trade-offs to achieve, for each specific application, the best compromise between performance parameters such as insertion loss, rejection, isolation, power handling, linearity, size and cost. RF filters are also used in radar and electronic and information warfare systems. For example, RF filters may be found in the RF front-ends of cellular base stations, mobile telephone and computing devices, satellite transceivers and ground stations, IoT (Internet of Things) devices, laptop computers and tablets, fixed point radio links, and other communications systems. RF filters are used in communications systems where information is transmitted over wireless links. A “stop-band” may be defined as a frequency range where the rejection of a filter is greater than a defined value such as 20 dB, 30 dB, 40 dB, or greater depending on application. For example, a “pass-band” may be defined as a frequency range where the insertion loss of a filter is better than a defined value such as 1 dB, 2 dB, or 3 dB. Specific requirements on a passband or stop-band depend on the specific application. A typical RF filter has at least one pass-band and at least one stop-band. The range of frequencies stopped by such a filter is referred to as the “stop-band” of the filter. The range of frequencies passed by a filter is referred to as the “pass-band” of the filter. Description of the Related ArtĪ radio frequency (RF) filter is a two-port device configured to pass some frequencies and to stop other frequencies, where “pass” means transmit with relatively low signal loss and “stop” means block or substantially attenuate. This disclosure relates to radio frequency filters using acoustic wave resonators, and specifically to filters for use in communications equipment. The copyright and trade dress owner has no objection to the facsimile reproduction by anyone of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever. This patent document may show and/or describe matter which is or may become trade dress of the owner. NOTICE OF COPYRIGHTS AND TRADE DRESSĪ portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent claims priority from provisional patent application 63/021,036, filed May 6, 2020, entitled XBAR WITH NO BUSBARS ON DIAPHRAGM, which is incorporated herein by reference.
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